Transmitted light streak scanner



Nov. 22, 1966 R. A. WRIGHT 3,286,567

TRANSMITTED LIGHT STREAK SCANNER Filed March 9, 1964 SORTER k CHOPPER 37 DE LA Y AMPL IF IE R Z gg Hl-PASSW 2 FILTER f u +/0 4 CHANNEL 2 lOOK W REF 60 CHANNEL 5{ VOLTAGE i IA CHANNEL 4 -55 as l T t: ""56 1 0 I a4 67 66 63 L REF VOLTAGE .SH/FT MULTI- A0055, 6/ REGISTER V/BRA TOR 1 :e5

ROBE]? T A. WRIGHT INVENTOR.

A T TORNE Y8 United States Patent 3,286,567 TRANSMITTED LIGHT STREAK SCANNER Robert A. Wright, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed Mar. 9, 11964, Ser. No. 350,377 6 Claims. (Cl. 8380) This invention relates to a transmitted light streak scanner and more particularly to a transmitted light detecting arrangement especially adapted to detect streak faults in translucent webbing material.

In the art of manufacture of webbing material and more specifically precision webbing material of the type having several coating thereon such as films for photographic purposes, various faults will occur from time to time in the surface or within the film or the coatings thereon during manufacture. When a fault is detected, the film containing that fault is separated prior to shipping good film-sheets. Some faults are relatively easily detectable by the reflectivity of the surface of the films as when faults such as holes in the coating and the like change the reflectivity of the surface substantially. Once a fault is detected in the film, the area of the fault may be marked as by a perforation or the fault signal may be retained in a memory device and applied directly to a sorter downstream of the fault detection arrangement after the film or webbing has been chopped or otherwise prepared in marketable form. One, film chopping and sorting apparatus is illustrated in the Patent 2,848,107 issued to I. H. Juengst and Howard J. Emerson and assigned to the assignee of the present application. However, it often occurs that a fault which may be serious to the final use of the webbing material is not easily detectable by surface inspection. This problem may arise when several layers, such as various photographic films require, are used with the fault occurring in an inner layer. A particular type of fault that is difficult to detect is a very narrow streak fault of the type which occurs when a bubble or a piece of dust and the like somehow lodges in the region of the roller or nozzle applying a coating to the film surface. Although these streaks are often of vary narrow dimensions, the final product will not react as it is designed because of this fault. In the case of X-ray films, for example, such a defect might seriously complicate interpretations of the image developed from that film.

Therefore, an object of the present invention is to provide a new and reliable streak fault detecting scanner.

In accordance with one embodiment of my invention a streak fault detector comprises an infrared light source or box which projects an infrared light beam against one side of a film being inspected. On the other side of this infrared beam region are provided a series of laterally spaced photocells particularly sensitive to the infrared light transmitted through the film. The photocells are arranged with a minimum axis being parallel to the line of motion of the film and are laterally oscillated at a rate of three cycles per second so that this minimum axis covers substantially all lateral portions of the film from time to time. The output of each of the photocells is passed through a three-cycle notch filter to block the oscillatory signal resulting from the motion of the photocell lenses themselves and then amplified in the frequency range of about 7 cycles per second to 100 cycles per second with a final output signal being applied to a delay circuit which ultimately operates :a sorter where the film is being prepared for packaging. In the meantime the film is traversing the region of inspection to a chopper and the chopped films output of the chopper go to the sorter where the delay signal will cause separation of any defective films.

3,286,567 Patented Nov. 22, 1966 The subject matter which is regarded as my invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. The invention, however, as to its organization and operation together with further objects and advantages thereof, will best be understood by reference to the following description taken in connection with the accompanying drawing, in which:

FIG. 1 is a simplified perspective view of the inspection station of my invention; and

FIG. 2 is a block diagram of the several circuits useable with the inspection station illustrated.

Referring now to the drawing, wherein like numbers refer to similar parts, I have shown in FIG. 1 a web 10 passing through an inspection station 11 where an infrared light beam impinges on one surface thereof. During one type of inspection operation the velocity of the web 10 is 340 f.p.m. The particular infrared beam of light used in this scanner is developed in a light box 12 having a plurality of masks 13 for determining the dimension of the beam at the inspection station 11, and a filter 14 for determining the composition of the light beam. In this particular case the filter may be one often referred to as 89B Wratten filter which allows passage of light of 7000 angstroms wavelength and longer and blocks all light below this wavelength. The light source itself is illustrated as a soft glow lamp 16 which produces a diffused light at the inspection station 11 whenever the web is moving.

Even with the system illustrated damaging exposure might result when the web 10 is stopped. Such exposure would cause developable salts within the emulsion and thereby expose the film or at least change its sensitivity to exposure. Because of this, I have provided a shutter 17 operable to allow transmission of light only so long as the web 10 is moving. A slipping clutch 18 coupling the shutter 17 to the transport system of the web 10 is a suitable shutter control for overcoming the bias of a spring 19 which tends to maintain the shutter 17 in a closed position. One lamp that operates well within this infrared light box is a watt Soft-Glow lamp marketed by General Electric. I have also found that certain fluorescent lighting is excellent for this use. When using tubular lighting the masks and the filter 13 and 14 respectively take the form of relatively long slits to reduce the problem of decreased light intensity at the edges of the film because of the edges greater distance from the light source.

The detector itself includes a plurality of photodetectors hereinafter referred to as photocells behind lenses 20 mounted on an oscillatory driveable platform 22 which is in turn driven by a motor 24 coupled thereto by :a rather large flywheel 25. In order to minimize the fniction of the system, I prefer to use an airbearing 26 thereunder supplied by an air conduit 27. Obviously Teflon guides and other low friction support techniques may be used in place of or supplementary to the system illustrated.

When the web is 10" wide and five photocells are used, the spacing between the centers of the lenses 20 is of the order of 2 inches. With the five lens systems illustrated, a 10" strip of webbing 10 may be easily scanned by providing for a 2" oscillatory stroke of the \guide 22. Care must be used to avoid scanning the edges of the film; about 9.8" scan is considered optimum.

The lenses and photodetectors therebehind are so oriented that .a major axis of the photodetectors is about As" long. The effective width of the photocells is .02". The scan pattern for one photocell is illustrated at 28 in dashed lines and is accomplished by a lens (each occurrence) having an image-to-object ratio of one. The lens system is arranged with sufficient depth of field so that minor film vibrations do not produce a significant magnitude of noise signal. It becomes obvious that a longitudinal streak, as illustrated at 30, will influence a major portion of this scan pattern should one of the patterns 28 :pass thereover. Even if the streak were very narrow, such a scan pattern would sense the difference in transmissivity because of the streak 30.

The output signals 31 developed by the photocells are passed through an amplifier 32 where they are increased in wattage sufificiently to be placed in a recording system indicated as a delay 34 and from there transferred to a sorter 36. In the meantime the web 10 has advanced [from the position shown in the direction indicated by the arrows 37 to a chopper 38 where the film including that containing a streak defect is cut into useable sheet from such as 10 X 12 inches and passed one at a time to the sorter 36. Idler rollers 39 maintain the web 10 during its passage through the illuminated region. As a defective sheet reaches the delivery portion of the sorter 36 a detected defect thereof will be transferred to the sorter from the delay means 34. Should no such signal arrive, this sheet will be placed with the stack of good film sheets. However, if an error signal is presented, this sheet is stacked with reject films.

Referring now to FIG. 2, I have shown in greater detail the electronic circuits necessary to sort and amplify the signals developed by the photocells 40. Each photocell 40 is coupled in a bias circuit including a resistor 42 so that the occurrence of a change of density in the web 10 will change the signal provided through a notch filter 44. The notch filter 44, of course, selectively blocks the changes of transmissiuity of the illuminated inspection station 11 resulting from the sweeping oscillatory motion of the rack 22. This 3 c.p.s. signal is blocked by the notch filter 44 so that the filter output includes only noise and other error signals which are then passed through :a low noise preamplifier 46 to a high pass filter 48. The high pass filter passes frequencies of the order of 7 cycles per second to 100 cycles per second to another amplifier 50. Both of the amplifiers 46 and 50 are carefully selected to be low noise amplifiers because of signal strength and the signal sensitivity of the system. Channels 2, 3, 4, and are provided with similar amplifiers, filters, etc.

As is known to those familiar wit-h streak faults, such defects are often of low signal intensity compared to several other types of defects. This is especially true if the fault occurs in a first or second layer of a multilayer emulsion. Therefore, the signal-to-noise ratio will limit the maximum sensitivity of the system. However, changes of density as small as /2% may be accurately detected using my invention. The particular amplifiers used as preamplifiers 46 and the amplifiers 50 of the several channels are low noise amplifiers known as Philbrick type -P65. The amplifiers 50 have a voltage gain of about to 70 and are usually seat at about when the several channels are balanced.

Balancing of the several channels is most easily accomplished by a uniform artificial signal. One method of developing such a signal is to place a fine wire vertically across the inspection station in front of each of the photocell lenses so that uniform shadows result. These shadows are then detected and the gain of the several channels is established at a level providing equal error indications.

The output of each channel of the several photocells is applied through silicon diodes 52 and 53 to common positive signal and negative signal bus lines 55 and 56 respectively. The signal bus lines are biased to a proper polarity and magnitude by reference voltage amplifiers 57 and 58 coupled to ganged variable voltage taps 60 and 61 of the DC. power supplies. Adjustment of the voltage taps 60 and 61 regulates the overall sensitivity of the system. The error signal occurring on the biased bus lines 55 and 56 are applied to an adder circuit 63 with one of the signals being inverted by a circuit 65 so that they are like polarity. The adder circuit output is again amplified in 'a P65 amplifier 66 and furnishes pulses to drive a multivibrator 67 which supplies reject signals to the delay device specifically called out as a shift register 34' as is how well known in the art for providing a delayed control signal to the sorter 36.

While I have shown and described particular embodiments of the present invention, other modifications may occur to those skilled in this art. For instance, the motor 24 may be run at a higher speed or the web 10 may be driven at a lower speed if it is deemed necessary to sweep substantially more than /2 cycle per sheet or if smaller sheets are to be provided. However, for the particular operation discussed herein, I prefer to use the velocities mentioned above where the chopper 38 separates 5 /3 sheets per second. vI intend, therefore, to have the appended claims cover all modifications which fall within the true spirit and scope of our invention.

I claim:

1. A streak fault detector for use with a moving translucent web comprising:

a light source for illuminating one side of the web as it moves past an inspection station;

photodetector means positioned to scan the other side of the illuminated portion of the web, said photodetector means being responsive to light transmission of the web in a narrow region of substantial length with the longest axis of the scan pattern being parallel to the movement of the web;

means for driving said photodetector means laterally relative to the web so that the scan pattern covers a substantial lateral portion thereof whereby longitudinal streak faults coming within the scan pattern will provide substantial signal variation to said photodetector means;

electronic circuit means receptive of signal information from said photodetector means including,

a notch filter to inhibit signals corresponding to any signal variations resulting from operation of said driving means, and

amplifier means receptive of the filtered signal information for developing a distinguishable error signal in response to a streak fault; and

sorter means for separating portions of the translucent web causing such error signals from other portions of the web.

2. A streak fault detector as in claim 1, wherein a plurality of photodetectors provide signals to a plurality of electronic circuit means respectively so that the stroke of said driving means is substantially less than the width of the translucent web, while said photodetectors collectively scan substantially the entire width of the web.

3. A streak fault detector for a moving translucent web comprising:

an infrared light source for illuminating substantially uniformly one side of the web as it is conveyed past an inspection station, the illuminated region including the entire width of the web and a substantial length thereof;

photodetector means;

lens means positioned to develop images on said photodetector means of a scan pattern portion of the other side of the illuminated region of the web, the scan patterns each being a narrow region of substantial length with the longest axis of the scan pattern being parallel to the movement of the web;

means for driving said lens means laterally relative to the web so that the scan pattern covers a substantial lateral portion of the web whereby longitudinal streak faults of the web coming within the scan pattern will provide substantial signal variation at said photodetector means;

electronic circuit means receptive of signal information from said photodectector means including,

a notch filter to inhibit signals corresponding to the cycling of said driving means, and amplifiers receptive of the filtered signal information for developing a distinguishable error signal in response to a streak fault; means for conveying the web through the inspection station so that adjacent longitudinal portions are illuminated and scanned; and a sorter means downstream of the inspection station for separating portions of the translucent web causing such error signals from other portions of the web. 4. A streak fault detector as in claim 3 wherein a plurality of lenses provide a plurality of images on a plurality of photodetectors which provide signals to a plurality of electronic circuit means respectively so that the stroke of said driving means is substantially less than the width of the translucent web.

5. A streak fault detector as in claim 3 including:

a chopper which separates sheets from the web at a predetermined rate, and the cycling of said driving means is at least one-half of such predetermined rate.

6. A streak fault detector for a moving translucent web comprising:

an infrared light source for illuminating substantially uniformly one side of the web as it is conveyed past an inspection station, the illuminated region including the entire width of the web and a substantial length thereof;

photodetector means;

lens means positioned to develop images on said photodetector means of a scan pattern portion of the other side of the illuminated region of the web, the scan patterns each being a narrow region of substantial length with the longest axis of the scan pattern being parallel to the movement of the web;

means for driving said lens means laterally relative to the web so that the scan pattern covers sequentially a substantial lateral portion of the web whereby longitudinal streak faults of the web coming within the scan pattern will provide substantial signal variation at said photodetector means;

electronic circuit means receptive of signal information from said photodetector means for developing error signals representative of such streak faults; and

a sorter means downstream of the inspection station for separating portions of the translucent web causing such error signals from other portions of the web.

References Cited by the Examiner UNITED STATES PATENTS 2,624,848 1/1953 Hancock et a1. 250-234 X 2,968,988 1/ 1961 Crosfield 250234 X 3,105,151 9/1963 Nash 250219 3,206,606 9/1965 Burgo et a1 250219 WILLIAM W. DYER, JR., Primary Examiner.

J. M. MEISTER, Assistant Examiner. 

1. A STREAK FAULT DETECTOR FOR USE WITH A MOVING TRANSLUCENT WEB COMPRISING: A LIGHT SOURCE FOR ILLIMINATING ONE SIDE OF THE WEB AS IT MOVES PAST AN INSPECTION STATION; PHOTODETECTOR MEANS POSITIONED TO SCAN THE OTHER SIDE OF THE ILLUMINATED PORTION OF THE WEB, SAID PHOTODETECTOR MEANS BEING RESPONSIVE TO LIGHT TRANSMISSION OF THE WEB IN A NARROW REGION OF SUBSTANTIAL LENGTH WITH THE LONGEST AXIS OF THE SCAN PATTERN BEING PARALLEL TO THE MOVEMENT OF THE WEB; MEANS FOR DRIVING SAID PHOTODECTOR MEANS LATERALLY RELATIVE TO THE WEB SO THAT THE SCAN PATTERN COVERS A SUBSTANTIAL LATERAL PORTION THEREOF WHEREBY LONGITUDINAL STREAK FAULTS COMING WITHIN THE SCAN PATTERN WILL PROVIDE SUBSTANTIAL SIGNAL VARIATIONS TO SAID PHOTODETECTOR MEANS; ELECTRONIC CIRCUIT MEANS RECEPTIVE OF SIGNAL INFORMATION FROM SAID PHOTODETECTOR MEANS INCLUDING, A NOTCH FILTER TO INHIBIT SIGNALS CORRESPONDING TO ANY SIGNAL VARIATIONS RESULTING FROM OPERATION OF SAID DRIVING MEANS, AND AMPLIFIER MEANS RESPECTIVE OF THE FILTERED SIGNAL INFORMATION FOR DEVELOPING A DISTINGUISHABLE ERROR SIGNAL IN RESPONSE TO A STREAK FAULT; AND SORTER MEANS FOR SEPARATING PORTIONS OF THE TRANSLUCENT WEB CAUSING SUCH ERROR SIGNALS FROM OTHER PORTIONS OF THE WEB. 